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  Electric
current is generated by the vibratory movement of electrons. Their
negative charge flux runs across the electric conductor in a determinate
order. In fact, depending on the type of electric current, one can
distinguish:
- direct currents, in which the direction of current (polarity)
does not change with time (accumulators);
- alternating currents, in which the direction periodically
changes at regular and constant time intervals (domestic, industrial,
road grids);
- impulsive currents, from electrostatic discharge or condenser.
At a parity of tension, alternating currents possess greater injurious
power than direct currents.
Each electric phenomenon is characterized by its generating motive power
(volt), its intensity (ampere), its frequency (hertz) and by the
resistance offered to the electronic movement by the conductor that
exerts a sort of friction (ohm). The current intensity is the main
determinant of its injurious character.
Besides the electric systems for lighting and energy, electrical equipment
and working tools for diagnosis and treatment are very commonly found
both in outpatients' deparments and in the wards.
Inadequate observance of safety instructions about electric systems or
erroneous employment of the related working tools can give rise to danger
from electricity both for the personnel and the patients.
Electric current effects on the human body depend on a variety of
correlated factors: current intensity, electric resistance of the human
body, current tension, current frequency, length of contact and current
route.
Electric risks in the hospital environment consist in:
- macroshock risks that follow the transit of electric current from
electric equipment and working tools through the skin;
- microshock risks that follow the introduction into the body of electric
currents of minimal intensity through catheters, probes, electrodes with
conductive properties.
The transit of electric current in the human body causes effects of
different gravity and consequences which are directly proportional to the
current intensity.
The lightest electric discharges (0.9-1.2 mA) cause tingling of the point
of contact (current perception threshold).
The medium intensity electric discharges (5-25 mA) cause muscular
contractions and localized painful cramps.
More intense discharges (25-80 mA) cause generalized muscular tetany
that, if prolonged by the contact with the conductor, can cause death by
asphyxia.
Definitely dangerous discharges are those of intensity 80mA-3A, because
they go through the heart causing ventricular fibrillation or other
severe alterations of the heart rate.
Further intensity discharges (3-8 A) depress neurological functions and
cause bulbar palsy with cardiorespiratory arrest.
Finally it must be remembered that electricity can cause burns by
electrothermic effect. These burns, although limited in extension, can
have severe prognosis for the late complications that they may yield.
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